Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')
Draft Class
Structure: Simple
Description
The product uses a more complex mechanism than necessary, which could lead to resultant weaknesses when the mechanism is not correctly understood, modeled, configured, implemented, or used.
Security mechanisms should be as simple as possible. Complex security mechanisms may engender partial implementations and compatibility problems, with resulting mismatches in assumptions and implemented security. A corollary of this principle is that data specifications should be as simple as possible, because complex data specifications result in complex validation code. Complex tasks and systems may also need to be guarded by complex security checks, so simple systems should be preferred.
Common Consequences 1
Scope: Other
Impact: Other
Potential Mitigations 1
Phase: Architecture and Design
Avoid complex security mechanisms when simpler ones would meet requirements. Avoid complex data models, and unnecessarily complex operations. Adopt architectures that provide guarantees, simplify understanding through elegance and abstraction, and that can be implemented similarly. Modularize, isolate and do not trust complex code, and apply other secure programming principles on these modules (e.g., least privilege) to mitigate vulnerabilities.
Demonstrative Examples 2
ID : DX-165
The IPSEC specification is complex, which resulted in bugs, partial implementations, and incompatibilities between vendors.HTTP Request Smuggling (Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) attacks are feasible because there are not stringent requirements for how illegal or inconsistent HTTP headers should be handled. This can lead to inconsistent implementations in which a proxy or firewall interprets the same data stream as a different set of requests than the end points in that stream.
Observed Examples 4
CVE-2007-6067Support for complex regular expressions leads to a resultant algorithmic complexity weakness (Inefficient Algorithmic Complexity).
CVE-2007-1552Either a filename extension and a Content-Type header could be used to infer the file type, but the developer only checks the Content-Type, enabling unrestricted file upload (Unrestricted Upload of File with Dangerous Type).
CVE-2007-6479In Apache environments, a "filename.php.gif" can be redirected to the PHP interpreter instead of being sent as an image/gif directly to the user. Not knowing this, the developer only checks the last extension of a submitted filename, enabling arbitrary code execution.
CVE-2005-2148The developer cleanses the $_REQUEST superglobal array, but PHP also populates $_GET, allowing attackers to bypass the protection mechanism and conduct SQL injection attacks against code that uses $_GET.
References 2
The Protection of Information in Computer Systems
Jerome H. Saltzer and Michael D. Schroeder
Proceedings of the IEEE 63
09-1975
ID: REF-196
Economy of Mechanism
Sean Barnum and Michael Gegick
13-09-2005
ID: REF-524
Applicable Platforms
Languages:
Not Language-Specific : Undetermined
Modes of Introduction
Architecture and Design
Implementation
Operation
Alternate Terms
Unnecessary Complexity
Related Weaknesses